2. Field of the Invention
The invention relates to an axial flow turbine with at least one row of individually adjustable guide vanes and at least one row of rotor blades, in which the guide vanes can be adjusted by means of an adjusting shaft, supported in a casing and passing through a vane carrier, and in which the tips of the rotor blades seal against a cover.
2. Discussion of Background
Such turbines are sufficiently known in the case of exhaust gas turbochargers, for example. As a control intervention to improve the acceleration and the torque behavior, guide vane adjustment on the turbine is, in addition to guide vane adjustment on the compressor, also a possible measure. One example of this is provided by EP 253 234 A1. The adjustable turbine guide vanes are intended to generate a larger heat drop for a given throughput. The turbine power, the turbine rotational speed and, finally, the boost pressure are increased by this means. So that the adjustable vanes do not jam during "hot" operation, they must, as a rule, be installed with an appropriate clearance. Particularly in the closed condition, the gap flow at the tip and the root of the vanes can greatly disturb the main flow in the duct. Since, furthermore, large fluid forces act on the adjustable vanes in the axial and peripheral directions, the vanes often have to be encastre at both the tip and the root in order to relieve the load on the adjusting shaft.
Furthermore, it is known art to match a turbomachine of a given size to a mass flow by varying the height of the blading.